the several- ffdif^i^in the Atfnosphere. 251 



hibc IS'" necessafy;*''bnt* th'at^'ls ju^t' wide 

 Enough to let air pass M^ater Without re- 

 quiring the tube to be agitated, fs best.— 

 I-.et little more nitrous gas than is suffici- 

 ent**) form nitric acid be admitted to the 

 oxygenous gas ; let no agitation be used ; and 

 as soon as the diminution appears to be over 

 for a moment let the residuary gas be traus^ 

 ferred to another tube, and it will remain 

 without any further diminution of consequence. 

 Tlien T-Tj. of the loss will be due to oxygen.— 

 The transferring ts necessary to prevent the 

 nitric acid formed and combined with the 

 Water, from absorbing the remainder of the 

 hitroUs gas to form nitrous acid! 

 "^'Sulphuret of lime is a good tes.t of the pro- 

 portion of oxygen in a given mixture, providecj 

 the liquid be not more than 20 or 30 per cent. 

 for the gas (atmospheric air) ; if the liquid 

 exceed this, there k a portion of azotic ga^j 

 imbibed somewhat uncertain in quantity. 



Volta's eudiometer is very accurate as well 

 as elegant and expeditious : according to 

 Monge, 100 oxygen require 196 measures of 

 hydrogen; according to Davy 192 ^ but frprn 

 the most attentive observations of my own, 185 

 arc sufficient.'' In atmospheric air I always 

 find W per cent, diminution when fired with 

 an excess of hydrogen; that is, TOO common 

 112 



